1. Field of the Invention
The present invention is generally directed to semiconductor devices, and, more particularly, to a method of making very thin dielectric layers for use in such devices.
2. Description of the Related Art
By way of background, an illustrative prior art transistor is depicted in FIG. 1. An illustrative semiconductor device 12 is formed above a surface 11 of a semiconducting substrate 10. The device 12 is formed within an active area 13 in the substrate 10 that is defined by the trench isolation 21. The illustrative semiconductor device 12 depicted in FIG. 1 is an NMOS transistor comprised of a gate insulation layer 16, a gate electrode 14, sidewall spacers 20 and source/drain regions 18. The various components of the illustrative transistor depicted in FIG. 1 may be formed by a variety of techniques, and they may be comprised of a variety of different materials.
In general, there is a constant drive to reduce the size of semiconductor devices and increase the operating speed of integrated circuit devices using such semiconductor devices. As feature sizes, e.g., channel length, decrease, other features of the transistor must also be decreased, or scaled down, e.g., the thickness of the gate insulation layer 16. Additionally, it is known that the drive current of the transistor, a parameter that determines how fast the device will operate, is inversely proportional to the thickness of the gate insulation layer 16. That is, all other things being equal, the thinner the gate insulation layer 16, the faster the device will operate. Thus, there is a desire for producing thinner gate insulation layers 16 of a sufficient quality to provide transistors with faster operating speeds. In many cases, the gate insulation layer 16 is comprised of silicon dioxide, although other insulating materials may also be used, e.g., an oxide, an oxynitride, silicon oxynitride, etc. Such layers have typically been formed by either a thermal oxidation process or a deposition process, such as a sputter deposition process, a chemical vapor deposition process, etc. However, currently available technology is limited in its ability to produce thin, high quality gate insulation layers 16 comprised of silicon dioxide. Additionally, there is a desire for a method and apparatus for forming very thin layers of material, e.g., silicon dioxide, as such layers may be used in several aspects of semiconductor processing, e.g., as gate insulation layers, in forming very thin sidewall spacers, etc.
The present invention is directed to a method that solves, or at least reduces, some or all of the aforementioned problems.
The present invention is directed to a method of forming very thin layers of dielectric materials in semiconductor manufacturing operations. In one illustrative embodiment, the method comprises providing a tool comprised of a process chamber, a lid above the process chamber, an RF coil for assisting in generating a plasma in the chamber, a substrate support, and a power supply coupled to the substrate support. The method continues with the step of positioning a substrate in the tool adjacent the substrate support and introducing a noble gas into the chamber. The method concludes with the step of forming a layer of material above the substrate by sputtering the lid material by performing at least the following steps: applying approximately 200-300 watts of power to the RF coil at a frequency of approximately 400 KHz and applying approximately 20-60 watts of power to the substrate at a frequency of approximately 13.56 MHz. In one particularly illustrative embodiment, the method disclosed herein is used to form a layer of silicon dioxide having a thickness ranging from approximately 7-10 xc3x85 at a rate of approximately 1 xc3x85/second.